Rear interlock

ABSTRACT

An interlock for a stack of drawers. A pair of drawer slides mounts each drawer, the interlock assembly being fitted to the rear of one of the drawer slides. A housing has a plate slidably supported thereon biased towards the rear of the slide. An actuator having an actuating surface co-operates with an actuator follower slidably supported in the slide member for movement at right angles to the movement of the plate. Releasable latching means extends between the housing and plate. Releasable catching means extend between the plate and the actuator. When a drawer is moved towards an open position, the catching means causes the plate to move to a blocking position where it can be held by the latching means, causing the actuating surface to co-operate with a follower surface on the actuator follower to move the actuator follower from a first position to a blocking position.

This invention relates to an interlock assembly for a drawer slide. Inparticular, this invention relates to an interlock assembly that ispositioned at the rear end of a drawer slide. In addition, thisinvention relates to an interlock assembly for use with a set ofvertically arranged drawers to prevent a drawer in the set of drawersfrom being opened while any other drawer in the set is open.

The invention also extends to an interlock assembly provided with a selfclose mechanism for the drawer slide to which it is fitted.

Items of furniture comprising drawers frequently have drawers, each ofwhich is mounted in a frame by means of a pair of slides. Such slidescomprise at least two slide members, which extend longitudinally and areslidable relative to one another. One slide member, usually the innermember, is attached to the drawer and the other slide member, usuallythe outer member, is attached to the frame of the item in which thedrawer is mounted. Often there is at least one intermediate slide memberpositioned between the outer and inner slide members. Usually, the slidemembers are slidably connected in that a bearing raceway of one slidemember nests within and interlinks with a bearing raceway of at leastone other slide member using ball bearings. The slide assembly helps toreduce friction between the drawer and the frame and, consequently,makes movement of the drawer easier and reduces wear on the components.

Where an item of furniture comprises more than one drawer, there is arisk that the item of furniture may tilt or topple over if more than onedrawer is open at any one time. Therefore, it is desirable to include inthe furniture an interlock, that is, a means for allowing a drawer to beopened only if no other drawer in the set of drawers is open, therebypreventing more than one drawer from being opened at any one time. Meansfor providing an interlock between drawers vertically arranged in aframe have been disclosed in the prior art. EP 0 818 597 A2 discloses aninterlock assembly for use with two or more vertically arranged drawersmounted on drawer slides. The interlock assembly is arranged at thefront of the drawer slide, that is, at the end nearest the drawer front.When a drawer is opened, actuator followers mounted in the outer orfixed slide member are pushed out from their position in the outer slidemember by an actuator and are kept in this position by the side edge ofthe inner slide member. The actuator followers are each attached to rodsand the movement of the actuator followers causes these rods to bepushed away from the slide, up and down, respectively. At the other endof each rod there may be an additional actuator follower. The movementof the rod pushes the additional actuator follower against the actuatorof the inner slide member of the drawer immediately below and/orimmediately above the drawer that has been opened. Accordingly, theactuator followers prevent the actuator on the front end of the innerslide member from sliding relative to the outer or fixed slide memberwhen another drawer is open. In this way the movement of the rods andactuators is transmitted to the drawers above and below the drawer whichis open so that all other drawers are prevented from opening by theaction of at least one actuator follower against the actuator for eachdrawer.

However, where an interlock assembly is situated at the front end of adrawer slide, the rods or other means for connecting the interlockassembly of the drawer slide to the interlock assemblies of a drawerslide above and/or below the drawer prevents a cover or shroud frombeing positioned around the drawer slide. Such covers are desirable foraesthetic reasons and consequently there is a need for an interlockassembly which will allow shrouds to cover the drawer slides.

Simply reversing the interlock assemblies of the prior art would notsolve this problem because, when the inner slide member moves relativeto the outer slide member, the actuator moves away from the rear end ofthe drawer slide and passes the actuator followers. Once the actuatorhas passed the actuator followers, there is nothing to keep the actuatorfollowers away from their original position in the outer slide member.Thus, other drawers in the vertical arrangement of drawer slides may beopened.

The present invention aims to provide an interlock assembly whichovercomes the above problems.

According to the present invention there is provided a drawer slideinterlock assembly for a drawer cabinet comprising a set of verticallyarranged drawers mounted in a frame by spaced drawer slides each havingan outer slide member and an inner slide member slidable relative to oneanother, the outer slide members being adapted for mounting on the frameand the inner slide members being adapted for mounting on respectiveones of the drawers, wherein said interlock assembly is located at therear of the extendible drawer slides, and comprises, for each drawerslide on at least one side of the set of drawers, a drawer slideinterlock assembly for a drawer cabinet comprising a set of verticallyarranged drawers mounted in a frame by spaced drawer slides each havingan outer slide member and an inner slide member slidable relative to oneanother, the outer slide member being adapted for mounting on the frameand the inner slide member being adapted for mounting on a respectiveone of the drawers, wherein said interlock assembly is located at therear of the extendible drawer slides, and comprises, for each drawerslide on at least one side of the set of drawers, a plate movablerelative to the outer slide member between a first position and ablocking position, an actuator mounted on the rear of the inner slidemember, catching means enabling the plate to be engaged by the actuatorto move it to its blocking position when the drawer to which the innerslide member is connected is opened, means for maintaining the plate inthe blocking position in the housing, an actuator follower supported formovement relative to the outer slide member between a plate blockingposition and a blocked position and wherein, when the drawer is opened,the actuator follower will be moved from its plate blocking position toits blocked position, said actuator follower subsequently beingmaintained in said blocked position while the drawer is open, andwherein closing of the drawer will cause the plate to be returned to itsfirst position, and the actuator follower will be allowed to return toits plate blocking position.

In the preferred arrangement, the actuator co-operates with the actuatorfollower to move the actuator follower outwardly away from thelongitudinal central axis of the outer slide member. However,co-operation could be between the plate and the actuator follower. Ineither of these arrangements, it is preferred that the actuator followeris maintained in said blocked position as a result of the plate beingheld in its blocking position as a result of moving to a latchedposition. Hence, when unlatching occurs, this will allow the actuatorfollower to return to its plate blocking position, because both theplate and the actuator will have returned to a “drawer-closed” position.Instead of being slidably mounted, the or each actuator follower couldbe mounted for rotary movement relative to the outer slide member.

Although the plate could be mounted for sliding movement directly in theouter slide member, e.g. on a suitable rail, it is preferred that theplate is slidably supported in a housing supported with a rear end ofthe outer slide member for movement parallel to said longitudinalcentral axis, said first position being at the rear of the housing, andthe blocking position being spaced therefrom. Preferably also, latchingmeans are provided between the housing and the plate.

Preferably, the drawer slide interlock assembly further comprises springmeans biasing the plate towards the rear of the housing, the latchingmeans extends between the housing and the plate to hold the plate in itsblocking position spaced from the rear of the housing, and the catchingmeans extends between the actuator and the plate, the catching meansbeing arranged to move the plate from the rear of the housing to itsblocking position when the inner drawer slide member is initially movedfrom its rearmost position when the drawer to which it is fitted isopened but being arranged to release the plate when the plate is in itsblocking position to allow the drawer fully to open, said releaseoccurring once the releasable latching means is in a latched position,the arrangement being such that when the drawer is moved towards aclosed position and the actuator moves into the vicinity of the latchedplate, the releasable latching means will be unlatched, thus allowingthe plate to move under its spring bias to the rear of the housing, andwherein the actuator follower has at least one follower surface thereonco-operating with a surface on the actuator to move the actuatorfollower to its blocked position, there being to a connecting rodattached to the actuator follower at one end and attached to a similaractuator follower of a drawer slide interlock assembly of an adjacentdrawer at its opposite end, the arrangement being such that, when theplate is in its blocking position, a side surface of the plate willprevent the actuator follower from moving back towards its plateblocking position, thus maintaining the actuator follower of theadjacent drawer slide interlock assembly of the adjacent drawer in sucha position that it will prevent movement of the plate of the adjacentmechanism from moving to its blocking position, thereby preventingopening of the second drawer.

In one embodiment, the plate is delta-shaped with a forward projectingnose and the leading edges of the delta-shape provide actuating surfaceson the plate.

In another embodiment, the plate is U-shaped with leading edges thereofforming actuating surfaces on the plate.

The actuator follower may have two follower surfaces thereon, a firstfollower surface co-operating the actuator surface on the actuator and asecond follower surface co-operating with a secondary actuating surfaceon the plate.

In one embodiment of the invention, the releasable latching means isformed partly on the projecting nose of the delta-shaped plate.

Preferably, the housing is divided into a rear part and a forward partspaced from the rear part and the rear part is connected to the forwardpart by at least one slide rail extending generally parallel to thelongitudinal axis of the outer slide member.

Preferably also, a slideway is provided on the underside of the platewhich engages with the or each slide rail of the housing.

It is preferred that a front edge of the rear part of the housing isparallel with a rear edge of the front part of the housing, said twoedges providing guide walls or slide channels for the or each actuatorfollower.

In the first embodiment of the invention, two rails preferably extendthe full length of the housing and the releasable latching meanscomprise an upstand at a forward end of one of the rails and a latchingnose on a forward end of the plate.

In the first embodiment, a front end of the plate preferably has thelatching nose and the plate catching means supported thereon, thelatching nose being connected to the remainder of the plate by a thinsection of plastics material acting as a pivot to allow the nose topivot about an axis extending at right-angles to the plane of the plate.

Preferably, the nose has a hook on a rear face thereof which co-operateswith a leading edge on the upstand to provide said releasable latchingmeans. Preferably also, a rear face of the upstand co-operates with astop on the plate to limit movement of the plate away from a rear end ofthe drawer slide.

In the first embodiment, the plate catching means preferably comprises astud, which is preferably offset, on a rear face of the actuator whichco-operates with a catching surface in a recess in the nose, the nosehaving a position of rest in which the hook is in a position to engagethe forward end of the upstand and the arrangement being such that, whenthe actuator moves towards the rear of the outer drawer slide member soas to overlie the plate, the stud will engage with a release surfaceopposite the, catching surface to cause the nose to pivot in a directionso as to release the hook from the forward end of the upstand thusallowing the plate to move under its spring bias towards the rear of theouter drawer slide member until the side surface of the plate will nolonger prevent the actuator follower from moving towards thelongitudinal central axis of the slide member.

The actuating surface on the actuator preferably comes into contact withthe first follower surface on the actuator follower before the actuatingsurface on the plate comes into contact with the second follower surfaceon the actuator follower. This ensures that movement of the actuatorfollower is started by the actuator. If such movement was started by theactuating surface on the plate, there is a risk that the resultantforces might unlatch the latching means as the inner drawer slide memberwas moved forwardly, or that the thin section of plastics materialacting as a pivot for the latching nose might break.

It is important that the actuating surfaces make an acute angle with thelongitudinal central axis; it is preferred that this angle be about 45°.

Preferably, the actuator has a further inclined surface on its trailingedge (relative to its forward movement) for co-operation with aninclined reset surface on the actuator follower. This is to allow themechanism of the interlock assembly to be reset or recycled if, for somereason, it should fall out of synchronisation, e.g. as a result ofaccidental unlatching of the latching means, or inadvertent release ofthe catching means at the wrong time.

In a second embodiment of the invention, it is preferred that the rearpart of the housing is connected to the forward part of the housing by abridging member incorporating two outwardly turned rails with which arear portion of the plate engages, there being upstanding guide postslocated on a forward end of the forward part of the housing which act asguide means for a forward end of the plate.

In this embodiment, the forward end of the plate is preferably providedwith laterally extending slide surfaces which engage beneath inturnedguides on the upstanding guide posts and the forward end of the plate isprovided with a central aperture therein to receive part of the catchingmeans.

Preferably, the part of the catching means is pivotally supported withinthe aperture by means of a pair of outwardly projecting pivots whichengage within mating pivot slots in the underside of the plate.Preferably also, the part of the catching means comprises a main spinewhich locates wholly within the aperture, the spine having upstandingfrom its rear end an abutment and upstanding from its front end afurther abutment having a chamfered leading edge, there being aresiliently deformable latching hook extending from the undersidethereof.

In the second embodiment of the invention, a groove is preferably formedon the rear face of the actuator which terminates in depending blocksized to fit between the abutment and the further abutment, a rear faceof the block being engageable with a forward face of the abutment and afront face of the block being engageable with a rear face of the furtherabutment, the arrangement being such that, as the actuator movesforwardly from a rear end of the outer drawer slide, the block willengage the rear face, thus drawing the plate against its spring biastowards a front end of the housing until a trailing end of the latchinghook engages with a front edge of the forward part of the housing,whereupon the block will disengage from the catching means to allow thedrawer to open fully, and the arrangement being such that, when thedrawer is moved rearwardly, the rear face of the block will ride overthe chamfered leading edge of the further abutment, allowing theactuator to move rearwardly until the block engages the forward face onthe abutment, thus causing the catching means to pivot so as todisengage the hook from the front edge of the housing, allowing theblock to engage between the abutment and the further abutment, andthereby allowing the plate to move under its spring bias towards therear end of the slide member.

In a third, preferred embodiment of the invention, a single slide railpreferably joins together the front and rear parts of the housing and acentral slide way is formed in said slide rail having at a rear endthereof a recycling recess and adjacent a front end thereof a latchingrecess. In this embodiment, it is preferred that the plate has a centralslide way on its underside which engages with the slide rail and,preferably within the central slide way, a recess provided at one endwith a pivot pin and at its opposite end with an arcuate slot whereby apivoting arm having an aperture in one end thereof and a catch pin atthe other end thereof is pivotally supported in the recess with theaperture surrounding the pivot pin and the catch pin sliding in thearcuate slot and projecting upwardly therefrom. Preferably also, adepending guide pin is provided on the underside of the pivot arm forsliding engagement in the slide way in the slide rail on the housing.

Preferably, the spring bias in the second and third embodiments isprovided by a coil spring extending between a buffer at the rear of thehousing and two spaced anchoring points on the underside of the plate.

In the preferred third embodiment of the invention, the actuatorpreferably has on its underside three principal recesses therein, two ofwhich open laterally outwards and are partly defined by forwardly facingactuating surfaces designed to cooperate with follower surfaces on theactuator followers and the third of which is located between tworearwardly facing inclined surfaces designed to cooperate with forwardlyfacing inclined follower surfaces on the actuator followers. The thirdrecess extends generally fore and aft within the underside of theactuator and has a downwardly depending island block therein spaced fromthe walls of the recess to define a fore and aft extending linearchannel on one side of the block and a recycling channel on the otherside. The fore and aft extending channel and the recycling channel areinterconnected at a forward end of the recess by an arcuate wall of therecess, part of which defines an unlatching surface for the catch pinand another part of which forms a recycling camming surface for thecatch pin. At its forward end, the island block has an inclined pinpulling surface which merges with a front end of a latch actuationsurface, the rear end of which merges with the fore and aft extendingpassageway. At its rear end, the depending island block has a recyclingsurface leading into the recycling channel.

The arrangement is such that forward movement of the actuator willresult in engagement of the catch pin by the pin pulling surface so asto move the plate towards a front end of the slide way in the slide railof the housing until the depending guide pin on the underside of thepivoting arm is biased by the inclined pin pulling surface andthereafter the latch actuating surface into the latching recess in theslide way, whereupon the actuator will become disengaged from the plateallowing full opening of the drawer. By virtue of the pivotal attachmentof the swinging arm on which the catch pin is supported to the plate,latching of the catch pin in the latching recess will result in theplate being moved to an actuator follower blocking position.

When the drawer is to be closed, the fore and aft extending passagewayon the underside of the actuator will slide over the catch pin locatedin the latching recess until the unlatching surface forming part of thearcuate forward end of the recess in the underside of the actuator willcause unlatching of the catch pin from the latching recess thus allowingthe plate to slide rearwardly preferably under the influence of itsspring bias out of the actuator follower blocking position until thecatch pin is at the rear end of the slide way in the slide rail of thehousing. By this time, the pin will have become engaged between acentral portion of the arcuate forward end of the recess and the pinpulling surface at the forward end of the depending island block, thusallowing the spring biasing the plate to its rearmost position in thehousing to pull the inner slide member and the drawer attached theretoto its rearmost position, thus acting as a self-closing mechanism.

Should the plate inadvertently move to its rearmost position in thehousing when the drawer is fully open due to the catch pin inadvertentlybecoming unlatched from the latching recess in the slide way, rearwardmovement of the actuator will result in a rearwardly facing recyclingsurface on the depending island block moving the catch pin upwardly intothe recycling recess in the slide way to allow the island block to movepast the pin whereupon the camming surface on the forwardly facingarcuate end of the recess in the underside of the actuator will move thecatch pin back into its central location at the rear of the slide way.

The invention also extends to a drawer having a drawer slide interlockassembly as described above, and to a stack of drawers arrangedvertically in a cabinet, each drawer being provided with an interlockassembly described above, there being a connecting rod extending betweenan actuator follower of the assembly of one drawer and that of anadjacent drawer, the rods being located adjacent the rear of thecabinet.

Also according to the invention, we provide a method of preventing astack of drawers supported in a cabinet from toppling over as a resultof more than one drawer being opened at any one time, comprising fittingeach drawer in the stack with a drawer slide interlock assembly asdescribed above, whereby when one of the drawers in the stack is opened,the interlock assembly will prevent the other drawers from being openeduntil the first drawer is moved to a closed position.

The drawer slide interlock assembly may have one or two actuatorfollowers. Where a drawer slide interlock assembly is incorporated intoa drawer slide that is located at the top or bottom of a set ofvertically arranged drawer slides, the interlock assembly may have oneactuator follower. Preferably, the drawer slide interlock assemblycomprises two actuator followers slidably mounted in the outer slidemember. Where there are two actuator followers, these are positioned onopposite sides of the longitudinal axis of the outer slide member.

Where the drawer slide interlock assembly is provided with two actuatorfollowers, each actuator follower may have a half width leg portion,shaped to co-operate with and be alongside a half width leg portion ofthe second actuator follower, each half width leg portion beingsufficiently long to extend beneath the slide rails of the housing tohold the actuator followers in position at all times.

Where the drawer slide has an intermediate slide member, the housing mayinclude at least one stop to prevent the intermediate slide member fromreaching the rear end of the outer slide member, and thus prevent itfrom interfering with the functioning of the drawer slide interlockassembly. Preferably, the rear end of the intermediate slide member hasa central cut away portion such that there are two prongs which extendfrom the rear end of the intermediate slide member and each of whichlocate against a stop on the housing when the intermediate slide memberis moved towards the rear of the housing.

The resilient means or spring biasing the plate towards the rear of thehousing may also provide the drawer slide with a pull-in mechanism. By“pull-in mechanism” is meant a self-close mechanism that assists thefinal movement of the drawer slide towards the closed position. In apreferred embodiment of the present invention, as the inner slide memberis pushed towards the rear of the drawer slide, the actuator overlapsthe plate, which is held there by the catching means extending betweenthe housing and the plate. When the inner slide member overlaps theplate, the catching means attaches the plate to the actuator.Consequently, the plate and actuator are pulled back together towardsthe rear of the drawer slide by the resilient means or spring extendingbetween the housing and the plate.

Also according to the present invention, we provide an interlockassembly for a drawer slide of one of the drawers of a set of drawersmounted on drawer slides in a cabinet, the interlock assembly beingprovided at the rear of the drawer slide, said interlock assemblyincorporating therein a self close mechanism for the drawer slide.

Preferably, the self close mechanism comprises a spring extendingbetween a housing of the interlock assembly and a plate movablysupported in the housing and which plate is connected to the inner slidemember of the drawer slide by latching means forming part of theinterlock assembly when the inner slide member is adjacent the rear ofthe drawer slide. Preferably, the plate is slidably supported in thehousing between a first portion at the rear of the housing and ablocking position spaced therefrom, the spring biasing the plate towardsthe first position at the rear of the housing.

Three embodiments of the present invention are now described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1 is a plan view of a housing for incorporation in an outer slidemember of a drawer slide according to a first embodiment of theinvention;

FIG. 2 is a plan view of a plate which is mountable on the housing ofFIG. 1;

FIG. 3 is a perspective view of an actuator follower;

FIG. 4 is a plan view of a drawer slide interlock assembly showing twoactuator followers in a plate blocking position and made up of thehousing of FIG. 1, the plate of FIG. 2, two actuator followers of FIG.3, all mounted on the rear of a drawer slide;

FIG. 5 is a plan view of the drawer slide interlock assembly of FIG. 1,with the drawer slide in a partially extended configuration and theplate in a latched, blocking position;

FIG. 6 is a partly schematic side elevation of three vertically arrangeddrawer slides, each comprising a drawer slide interlock assembly, withthe top drawer slide in a partially extended configuration resultingfrom partial opening of a drawer to which it is fitted, and its plate ina latched, blocking position, thus preventing opening of the other twodrawers;

FIG. 7 is a plan view similar to FIG. 1 but of a housing of a secondembodiment of the invention;

FIG. 8 is a plan view of a plate and catching means for the secondembodiment;

FIG. 9 is a side view of the catching means removed from the plate;

FIG. 10 is an end view of the plate of FIG. 8;

FIG. 11 is a side view corresponding to FIG. 8;

FIG. 12 is a plan view showing the plate and catching means mounted onthe housing of FIG. 7;

FIG. 13 is a plan view of a housing of an third embodiment of theinvention;

FIG. 14 is a plan view of a plate and catching means for the thirdembodiment;

FIG. 15 is an underneath view of the plate and catching means;

FIG. 16 is an underneath view of the plate, with the catching meansremoved;

FIG. 17 is a plan view of the catching means;

FIG. 18 is a side view of the catching means;

FIG. 19 is a plan view similar to FIG. 4, but of the third embodiment,showing the housing, plate and catching means and two actuator followersin a plate blocking position assembled in the rear of an outer slidemember, with the plate biased to its rearmost position in the housing,and with an actuator connected to the rear end of an inner slide membershown in ghost in its position of use when a drawer to which it isfitted is in a closed position, and the actuator is overlying the plateand housing;

FIG. 20 is a view similar to FIG. 19, but showing the relative locationsof the parts after the drawer has been opened a small amount; and

FIG. 21 is a view similar to FIG. 5, but corresponding to FIGS. 19 and20, and showing the relative positions of the parts when the drawer hasbeen opened further, and the catching means has been moved to a latchedposition, in which the plate is in an actuator follower blockingposition.

Referring to FIGS. 1 to 6 of the drawings, FIG. 5 shows a drawer slideinterlock assembly (10) incorporated into the rear end (20) of a drawerslide (12). The drawer slide has an outer slide member (14), an innerslide member (16) and an intermediate slide member (18). The assembly(10) includes an actuator (32) mounted on the rear end (34) of the innerslide member (16). The actuator has two leading, inclined actuatingsurfaces (58, 60) and two further inclined surfaces (62, 64) on itstrailing end (66) and a stud (82) located on the face of the actuatorfacing the outer slide member. As shown, the actuator is formed of ahard polymeric member (59) supported on the rear end (34) of the member(16).

The assembly (10) includes a housing (22) which is mounted at the rearend of the outer slide member (14). The housing shown in detail in FIG.1 is made from polymeric material and comprises a rear part (23) andspaced therefrom, a forward part (25) connected together by twoupstanding, central rails (74) on which a delta-shaped plate (26), whichis shown in FIG. 2, is slidably mounted. The plate (26) may slidebetween a rear edge (24) of the housing and a position spaced from therear edge (26) with a spring (50) biasing the plate towards the rearedge (24). However, the spring (50) is not essential.

A catching means (30) extending between the housing (20) and the plate(26) holds the plate away from the rear edge (24) of the housing (22)and comprises an upstand (78) that is part of the housing and upstandsfrom a front portion of one of the rails (74). The top surface of theupstand (78), when the plate (26) is assembled with the housing, asshown in FIGS. 4 and 5, lies substantially in the plane of the top ofplate (26). The catching means further comprises a hook (76) and a stop(84) on the plate (26). One end (86) of the spring (50) is attached tothe housing (22) and the other end (88) of the spring is attached to theplate (26). Two inwardly directed stops (27) form abutments on thehousing (22) which limit rearward movement of the plate (26). Forwardmovement is limited by the stop (84) on the plate (26) co-operating witha rear face of the upstand (78).

On the underside of the plate (26), there are two grooves defined byinturned lower flanges and the underside of the plate itself which forma slideway and hold the plate captive on the rails (74), the railshaving laterally outwardly extending flanges thereon beneath which thelower flanges on the underside of the plate engage.

The plate (26) has a rear edge (28), two inclined front edges which formsecondary actuating surfaces (68 and 70), and two side edges (96 and 98)and a forwardly projecting nose (79) resiliently connected to a frontend of the plate by a thin section of polymeric material (81) allowingthe nose (79) to pivot about an axis extending at right angles to theplane of the plate (26). The hook (76) is formed on the nose (79). Theplate fits between the slide tracks (15, 17) of the outer slide member.The plate (26) also has a recess (80) formed in a side face of the nose(79) which co-operates with the stud (82) on the actuator (32) to forman attaching means between the plate (26) and the actuator (32). Therecess (80) has a release surface (83) and a catching surface (85).

Two actuator followers (36) are slidably mounted in the outer slidemember (14) for lateral movement at right angles to the movement of theinner slide member (16), the followers (36) having portions extendingoutwardly on the outer slide member (14), through apertures in the slidetracks of the outer slide member. The actuator followers (36) aremounted on opposite sides of and extend substantially perpendicularly tothe longitudinal axis of the outer slide member (14), such that theyface each other. The actuator followers of the embodiment shown in FIGS.1 to 6 may be more clearly seen in FIG. 3, and are guided laterally bytwo parallel spaced guide walls provided by, respectively, a front wallof the rear part (23) of the housing (22) and a rear wall of the forwardpart (25). Each actuator follower is provided with means (54) by whichit may be connected to an interlock rod (40, 40 a), as shown in FIG. 6.Each follower (36) has an internal half width leg (56), and upstandingcentrally therefrom, a turret (55). The half width legs 56 overlap withone another when the followers are mounted in the housing 20 (see FIG.4), and extend beneath the rails (74) to hold the followers (36) inplace. The turrets have an inwardly facing upper or first followersurface (46) and an inwardly facing lower or second follower surface(48) spaced laterally outwards from the surface (46). The two followersurfaces (46, 48) are inclined at an angle of about 45° to thelongitudinal axis of the outer slide member (14). The upper or firstfollower surface (46) is substantially in the same plane as the actuator(32) whereas the lower or second follower surface (48) is mainly in thesame plane as the plate (26).

At its rear end, a cut out (71) is provided in the intermediate slidemember (18) to accommodate the front ends of the rails (74) and of theplate (26), leaving two prongs (72) which extend from the rear end ofthe intermediate slide member. These prongs locate against respectivestops (52) moulded into the housing (22), when the intermediate slidemember is moved to a closed position.

The drawer slide interlock assembly works as follows:

When a drawer (not shown) attached to the drawer slide is in a closedposition, the drawer slide will be as shown in FIG. 4 and the interlockassembly is inoperative. When the drawer is opened, the inner slidemember (16) is eventually moved away from the rear end (20) of thedrawer slide, the stud (82) on the underside of the actuator (32) willengage the catching surface (85) of the recess (80), thus pulling theplate (26) away from the end (20) of the drawer slide. As the innerslide member and the plate (26) move forwardly, the upper or firstfollower surfaces (46) on each actuator follower will be engaged by thesurfaces (58, 60) respectively of actuator (32), thus starting to movethe followers (36) away from the central longitudinal axis of the drawerslide, so as to move the followers (36) laterally outwards.

Continued forward movement of the actuator (32) will then result in thelower or second follower cam surfaces (48) on the followers (36)becoming engaged respectively by the actuating surfaces (68, 70) on theplate (26), with the result that the followers are moved laterallyoutwards further. It is important that engagement of the followersurfaces occurs in the above described way, otherwise the resultantforces between the stud (82) and catching surface (85) may result indisengagement therebetween, or alternatively, the force on the line ofweakness (81) may result in breakage at this point.

As the inner slide member continues to move away from the rear end (20)of the drawer slide, and the plate continues to slide along rails (74),the hook (76) will slide along the side of the upstand (78). When thehook reaches the forward end of the upstand (78), the hook will swingclockwise, due to the resilient connection (81) of the nose (79) to therest of the plate (26), and wrap round the end of upstand (78), and actas a latch which prevents the plate (26) from sliding back towards theend (20) of the drawer slide under the action of the spring (50). Plate(26) is prevented from moving further away from the end of the drawerslide by stop (84), which abuts the end of the upstand (78). Theclockwise swinging of the nose (79) disengages the hook (76) from thestud (82), thus allowing the inner slide member to continue moving awayfrom the rear of the drawer slide and pass through the intermediateslide member (18). This configuration is shown in FIG. 5, where thedrawer slide is in a partly extended configuration, with the drawer (notshown) partially open.

Referring now to FIG. 6, each drawer slide interlock assembly isconnected to its adjacent assembly by a connecting rod (40 and 40 a),the arrangement being such that one end of each connecting rod (40) isconnected to the means (54), e.g. inserted into an aperture in anactuator follower (36) of one drawer slide interlock assembly and asecond end (44) of the connecting rod (54) is inserted into anequivalent means (54) on an actuator follower (36) of the adjacentassembly.

This means that, when the upper drawer is open, it is not possible toopen either of the drawers (not shown) attached to the middle or bottomdrawer slide interlock assemblies. The inner slide member of the middledrawer slide is prevented from moving because the top actuator follower(36) of the middle drawer slide interlock assembly is not able to movefrom its blocking position, as the actuator follower at the other end ofthe connecting rod (40) to which it is attached is prevented from movingby the presence of edge (96) of plate (26). Similarly, the bottom drawercannot be opened because the inner slide member of the bottom drawerslide is prevented from moving because the top actuator follower (36) ofthe bottom drawer slide interlock assembly is not able to move from itsblocking position as the actuator follower (36) at the other end of theconnecting rod (40 a) to which it is attached is prevented from movingby the interaction between the legs (56) of the actuator followers ofthe middle drawer slide interlock assembly which, as described above,are unable to move due to the presence of edge (96) of plate (26)blocking the movement of the bottom actuator follower (36) of the topdrawer slide. In this way, opening one drawer in a set of verticallyarranged drawers causes the blocking of the movement of the inner slidemember of the other drawer slides. Although not shown here, a similareffect may be achieved with all the drawers in a set of verticallyarranged closed drawers by operating a lock to force down or up thehighest or lowest actuator follower (36), respectively, in the set ofdrawer slide interlock assemblies, in order to lock the drawers in aclosed position, as described subsequently herein.

Referring now to FIGS. 7 to 12, which illustrate a second embodiment ofthe present invention, parts similar or identical to those of the firstembodiment are identified by the same reference numerals. As in theprevious embodiment, a housing (122) is fitted into a rear end of theouter slide member (14) which is provided with cut-outs (123) for thispurpose. The housing is made of a polymeric material and comprises arear part (124) spaced from a forward part (126) and joined thereto by abridging member (128) incorporating two out-turned rails (130, 132) onwhich a delta-shaped plate 134) may be slidably located (see FIGS. 8 and10 to 12). For this purpose, the plate (134) is provided at its rear endwith a slide way (136) as illustrated in FIG. 10.

Outwardly projecting lugs (138) on the housing hold the housing in theopenings (123) in the outer slide member (14), a similar arrangement towhat is provided in the first embodiment described above. Towards thefront end of the front portion (126) of the housing, upstanding guideposts (140) are provided, the guide posts having inturned portions (142)which act as forward guideways for the front end of the plate (134)which is provided with laterally extending slide surfaces (144) whichlocate beneath the portions (142) and between the posts (140). At itsrear end, the housing (20) is provided with an upstanding arcuate buffer(146) against which a central nose on the underside of the plate (134)can engage to limit rearward movement of the plate (134) in the housing(20). Further arcuate buffers (150) are provided on an upstandinginternal wall of the forward portion (126) of the plate to limitrearward movement of the intermediate slide member (18) of the drawerslide.

As can be seen, particularly from FIG. 8, the plate (134) is providedwith two sets of inwardly turned guides (152, 154) which co-operate withthe rails (130, 132) on the bridge (128) of the housing (120) to allowthe plate (134) to slide in a controlled manner relative to the housing.A spring (not shown) extends between the buffer (146) on the housing(20) and the plate (134) to bias the plate towards the rear of thehousing (20). Two anchoring points (155) are provided on the undersideof the plate (134) to which the ends of the spring are connected. Thespring is not essential, but preferred, not only to bias the plate (134)towards the rear of the housing (20) but also so as to provide a selfclosing feature for the drawer slide when it approaches its fully closedposition (the spring (50) in the first embodiment provides a similareffect).

At its forward end, the plate (134), between the slide surfaces (144),is provided with a central aperture (156) to receive a catching means(158) seen in side elevation in FIG. 9. The catching means is pivotallyconnected to the plate (134) by means of two outwardly projecting pivots(160), one on either side thereof, which engage with a snap fit withinmating pivot slots formed in the underside of the plate (134). Thecatching means (158) has a main spine (162) upstanding from a rear endof which is an abutment (164) and upstanding from a front end of whichis a further abutment (166), a leading edge of which is chamfered (asshown at 168). This catching means is engageable with a centrallylocated depending block on the underside of the actuator (32), thelength (X) of which corresponds to the spacing (X) between the abutments(164, 166). Projecting from the underside of the forward end of thecatching means (158) is a resiliently deformable latching hook (170).When in its relaxed position, the free end (172) of the latching hook(170) will abut a forward end (174) of the housing (20) when the plate(134) together with the catching means (158) supported therein is pulledforwardly when a leading face (85) of the block (83) on the actuator(32) mounted in the inner drawer slide member (16) engages the face(166) on the catching means (158). When the faces (172 and 174) areabutting one another, side edges (96) of the plate (134) will be locatedin line with the recesses (123) in the outer slide member (14) as in thefirst embodiment of the invention, thus preventing actuator followers(36 a) from moving inwardly towards a central longitudinal axis of theouter slide member (14). As with the first embodiment of the invention,the plate (134) is provided with forwardly facing actuating surfaces(68, 70) which engage with inwardly and rearwardly facing followersurfaces (48) on the followers (36 a) when the plate (134) is pulledforwardly by forward movement of the inner slide member (16). This ofcourse has the effect of moving the followers (36 a) outwardly away fromthe longitudinally axis of the outer slide member (14).

As in the previous embodiment, each of the followers (36 a) is connectedin the manner shown in FIG. 6 by rods (40, 40 a) to followers ofadjacent slides so that if one drawer of a stack attached to an innerslide follower is opened, this will then make it impossible for theother drawers in the stack of drawers to be opened as describedpreviously.

When it is desired to close the drawer, rearward movement of the innerslide member (16) will result in a groove (89) on the rear face of theactuator sliding over the abutments (164, 166) until a rear face (87) onthe block (83) rides up over the chamfered surface (168) of the upstand(166), thus allowing the actuator (32) to move further rearwardly untilthe rear face (87) hits a forward facing surface (176) of the rearupstand (164) of the catching means. This will immediately cause thecatching means (158) to pivot (anticlockwise as shown in FIG. 9) aboutits pivots (160), thus moving the free edge (172) of the latching hook(170) out of engagement with the front edge (174) on the housing,whereupon the spring (not shown) will immediately cause the plate (134)to move rearwardly in the housing (20) until prevented from moving anyfurther by the upstanding buffer (146). This rearward movement will ofcourse move the two lateral surfaces or side edges (96) of the plate(13) rearwardly, away from the recesses (123), thus allowing each of thefollowers (36) to move inwardly towards the longitudinal axis of theouter slide member (14), thus subsequently permitting another drawer inthe stack of drawers to be opened. It will thus be appreciated that theinterlock assembly shown in FIG. 7 to 12 operates in a similar manner tothat shown in FIGS. 1 to 6 although the latching arrangement for holdingthe plate (134) in its forward interlocking position operates in adifferent manner from that shown in FIGS. 1 to 5.

Referring now to the third embodiment of the invention illustrated inFIGS. 13 to 21, the interlock assembly includes a housing (222) whichfits into the rear end of an outer slide member (14) which is providedwith cut outs for the purpose, with a snap fit, as in the previousembodiments. The housing is made of a polymeric material and comprises arear part (224) spaced from a forward part (226) which are joinedtogether by a slide rail (228) for slidably supporting, for fore and aftmovement, a generally U-shaped plate (234). The slide rail (228)terminates at its rear end in an upstanding buffer (246), on an outerarcuate face (248) of which an arcuate groove is formed to accommodate acentral portion of a spring (250). The slide rail (228) has a centralslideway (230) therein towards a front end of which there is a latchingrecess (231) and at the rear end of which there is a recycling recess(235). As in the previous embodiments, a pair of actuator followers(236) is slidable supported in slide channels (237) in the housing (224)for sliding movement at right angles to the longitudinal axis of theouter slide member (14). Although the actuator followers are shown asbeing slidably supported in slide channels (237) formed in the housing(222), it will be appreciated that the actuator followers could besupported in some other way for sliding movement at right angles to thelongitudinal axis of the outer slide member, not only in this embodimentbut also in the previously described embodiments. As in the previousembodiments, the actuator followers are provided with follower surfaces(47 and 48), and with means (54) for connection to interlock rods (40and 40A). Outwardly projecting lugs (238) hold the housing (222) firmlyin the outer slide member (14), as in the previous embodiments.

As can be seen from FIGS. 14 to 18 in particular, the plate (234) canslide back and forth on the housing (222) and has a central slideway(249) running throughout its length which engages the slide rail (228)to guide the plate in its fore and aft sliding movement. Projectingupwardly from an upper face of the plate is a pair of anchoring pegs(255) to which respective ends of the spring (250) are attached. Thisensures that at all times the plate is biased towards to its rearmostposition in the housing, as shown in FIG. 19. Down each outer side edgeof the plate is a longitudinally extending guideway (254) which engageswith an inwardly projecting guide rib (252) on an internal wall of thehousing (222) so as to ensure linear sliding movement of the platerelative to the housing. A recess (257) is formed in the underside ofthe plate (234) having a depending pivot pin (259) at one end and anarcuate slot (261) adjacent an opposite end thereof. A catching means inthe form of a pivoting arm (263) is loosely supported within the recess(257), the pivoting arm having adjacent one end thereof an aperture(265) therein which forms a close fit on the pivot pin (259) and havingat its upper end a catch pin (267) which forms a sliding fit in thearcuate slot (261). The catch pin (267) projects upwardly through theslot (261) by a sufficient distance to enable it to be engaged by anactuator (232) secured to the rear end of the inner slide member (16).Also extending downwardly from the pivoting arm (263) is a dependingguide pin (269) which is coaxial with the catch pin (267) and forms asliding fit in the slideway (230) in the housing (222).

Referring now to FIGS. 19 to 21, the actuator (232) has three principalrecesses on its underside, one on its trailing central region and twoopening outwardly on either side towards the sides of the outer slidemember (14). Each of the outwardly opening recesses is shaped to providea pair of forwardly extending but inclined actuating surfaces (258, 260)which are designed to cooperate with respective ones of the followersurfaces (48) on the actuator followers (36). Furthermore, the trailingor rear end of the actuator (232) is also formed with inclined surfaces(62, 64) as in the previous embodiments which cooperate with thefollower surfaces or recess surfaces (47) on the follower (36).Supplementary recesses (201) are also formed in the underside of theactuator (232) to make certain that when the actuator is in its rearmostposition, its underside does not foul the tip of the upstanding springanchoring pegs (255).

Between the inclined surfaces (62 and 64) the central recess identifiedat 203 in FIGS. 19 to 21, has a depending generally centrally locatedisland block (205) therein spaced from the opposed specially shaped sidewalls (207 and 209) of the recess by a distance sufficient toaccommodate with an easy sliding fit the upstanding end of the catch pin(267). The island block (205) has a leading inclined pin pulling surface(211) which merges with a less sharply inclined pin camming surface(213) at one end thereof, the opposite end thereof merging with a foreand aft extending surface (215) parallel to but spaced from the sidewall (209). At its trailing end, the island block (205) has an inclinedrecycling surface (217) extending generally parallel to the surface(213) which then merges with an arcuate side wall surface (219) which isgenerally parallel to but spaced from the arcuate side wall (207)defining the recess (203), so as to provide a recycling channel (221)which is just sufficiently wide to accommodate the projecting tip of thecatch pin (267). Between the parallel side walls (209 and 215) on theother side of the island block, there is a fore and aft extendingchannel for the catch pin (267) and opposite the latch actuation surface(213) there is a pin unlatching surface (223) designed to move the catchpin (267) out of the latching recess (231) formed in the slide way(230).

The mechanism operates as follows:

When the drawer to which the inner slide member (16) is attached is inits closed position, the actuator (232) will be in its FIG. 19 positionand the plate (234) will be in its rearmost position in the housing(222). When in this position, the catch pin (267) will be centrallylocated between an arcuate forward end (225) of the recess (203) and therearwardly extending inclined pin pulling surface (211) of the islandblock (205). Forward movement of the drawer to open the drawer willcause the pin pulling surface (211) to engage the rear of the catch pin(267). The pin pulling surface (211) is slightly inclined, thus tendingto bias the pin and hence the pivoting arm (263) to which it is engagedto move downwardly as shown in the figures but because there is afurther depending guide pin (269) on the pivoting arm (263) which isengaged in the slide way (230), the two pins and the pivoting arm (263)have to remain in a central position. Accordingly, continued movement ofthe inner slide member (16) as a result of further opening of the drawerto which it is connected will result in the plate in which the pivotingarm is pivotally supported to move forwardly against the bias of thespring (250) towards the front end of the slide way (230). However, asthe plate (234) nears the front of the slide way (231), the presence ofthe latching recess (231) allows the downward biasing force on the catchpin (267) to move the depending guide pin (269) downwardly into thelatching recess (231), this downward movement being completed by theinclined latch actuation surface (213) as the inner slide member (16)moves further forwardly. Once the depending guide pin has been forcedwholly into the latching recess (231) by the latch actuation surface(213), it will be held within the latch recess (231) because therearmost side wall of the latching recess (231) is slightly inclined asshown at 202. Once the depending guide pin is latched within thelatching recess (231), it will then be located wholly within the foreand aft extending passageway defined by the side walls (209 and 215),thus allowing the inner slide member (16) and the drawer to which it isattached to be fully opened since the pin (267) can escape from therearmost end of the aperture (203). This configuration is clearlyillustrated in FIG. 21, whereas FIG. 20 shows the mechanism in anintermediate position between the positions of FIGS. 19 and 21.

Forward movement of the plate (234) as a result of opening of the drawerto which the inner slide member (16) is attached will cause inclinedforwardly facing actuating surfaces (68 and 70) on the plate (234) orthe forwardly facing actuating surfaces (258 and 60) on the actuator tomove into engagement with the follower or reset surfaces (248) on thefollower (36) so as to move the followers outwardly away from thelongitudinal central axis of the outer slide member (14). This will thenallow the plate (234) to move freely forwardly as a result of furtheropening of the drawer to which the inner slide member (16) is attachedso that two opposed side edges (296) of the plate then prevent inwardmovement of the actuator followers (36).

Of course, once the actuator followers (36) are held in their outermostblocked position, as described above, rods attached at one end to theactuator followers (36) and connected at their other ends to actuatorfollowers of adjacent drawer slides fitted with identical mechanismswill block the forward movement of the respective plate (234), thuspreventing the adjacent drawers from being opened, as in the previousembodiments.

When it is desired to close the drawer so as to move the mechanism fromthe FIG. 21 position, rearward movement of the drawer will eventuallycause the actuator (232) attached to the inner slide member (16) of thedrawer to move to a position wherein the mouth of the aperture (203)will overlie the open end of the slide way (230). Because the catch pin(267) is latched within the recess (232), the fore and aft extendingpassageway defined by the side walls (209 and 215) will move over theprojecting tip of the catch pin (267) until eventually the unlatchingsurface (223) engages the tip of the pin (267) and, acting as a cam,starts to lift the pin out of the latching recess (231). Continuedrearward movement of the actuator will lift the catch pin totally out ofthe recess (231) and the latch pin will be caused to move between thearcuate forward end (225) of the wall of the recess (203) and the pinpulling surface (211). Once the pin is in this position, the spring(250) will bias the plate and hence the actuator which is now engagedwith the plate by virtue of the presence of the pin (267) engaging thesurface (225) towards the rear of the outer side member (14) thus actingas a self-closing mechanism for the drawer. Of course, as the plate(234) moves back to its rearmost position, as illustrated in FIG. 19, sothe side edges (296) thereof will move to the rear of the slide channels(237) thus allowing the actuator followers (36) to move inwardly towardsthe longitudinal central axis of the outer slide member. In other words,should a user wish to open an adjacent drawer of the stack of drawers,this will be possible since the interlock mechanism of the drawer to beopened will be allowed to operate so as to move one or other of theactuator followers (36) into a plate blocking position as shown in FIG.19.

In some instances, it is possible for the catch pin (267) to becomeinadvertently disengaged from the latching recess (231) even when thedrawer is fully opened and the actuator (232) is nowhere near thehousing (222) let alone the slide way (230). When such unlatching of thecatch pin occurs, the spring (250) will of course immediately return theplate (234) together with the catch pin and its pivoting arm back to theFIG. 19 position. In that event, subsequent closing of the drawer willeventually result in the inclined recycling surface (217) on thetrailing edge of the island block (205) coming into engagement with thecatch pin (267). Such engagement will result in the catch pin (267)being cammed by the inclined surface (217) upwardly into the recyclingrecess (235). When this occurs, the pin can then pass down the channel(221) as a result of further rearward movement of the actuator (232)until the pin moves into the inwardly inclined region of the passageway(221) whereupon it will be cammed back to a central location in themiddle of the slide way (230) by virtue of a camming surface (227)forming part of the arcuate forward end (225) of the recess (203). Oncethe catch pin (267) is centrally located in the slide way (230), it willbe located behind the pin pulling surface (211) thus allowing themechanism to operate as previously described. This moving aside of thecatch pin to allow the passage of the island block (203) is known asrecycling. Such recycling is also possible in each of the previouslydescribed embodiments.

In each of the embodiments described herein, two further inclinedsurfaces (62 and 64) are provided on the actuator (32) on the rear endthereof which co-operate respectively with inclined reset surfaces (47)on the followers (36, 36 a). This means that, when the actuator (32) isreturned to the rear of the drawer slide on closing a drawer to whichthe drawer slide is fitted, the two followers will be moved to anon-blocking position spaced from the longitudinal axis of the drawerslide, should they inadvertently have moved to a plate blockingposition.

It will be appreciated that, in the second embodiment of FIGS. 7 to 12,the actuator followers (36 a) may be provided with two sets of followersurfaces (46, 48) as in the first embodiment of the invention. Also, inthe second embodiment, small projections (180) extend onto the spacebetween the rear part (124) and forward part (126) of the housing, whichco-operate with projections (not shown) on the followers (36 a). Thisallows the followers to be fitted by forcing the projections thereonpast the projections (180) with a “snap-fit” action.

It is envisaged that at its rear end, the housing (20) may be fittedwith a cantilevered, forwardly extending plate which will overlie theactuator when it is located at the rear of the drawer slide, to preventlateral play of the actuator, and hence of the closed drawer to which itis fitted.

It is also envisaged that the rear part (24, 124) of the housing neednot be supported by the outer slide member (14).

It will be apparent to those skilled in the art that some of thefeatures described with reference to the first embodiment of theinvention could be used on one or both of the second and thirdembodiments of the invention, and vice versa.

The interlocking assemblies described herein can also easily be providedwith a locking capability by interfacing with a separate locking systemor mechanism. For example, a locking system may comprise a member whichblocks the upward displacement of the actuator followers, therebypreventing any of the slide members from opening. This can beaccomplished by using a lock member which can slide in front of thetravel path of a rod connected to the upper actuator follower of theuppermost slide member.

It will of course be understood that the present invention has beendescribed above purely by way of example, and modifications of detailcan be made within the scope of the invention.

1. A drawer slide interlock assembly for a drawer cabinet comprising aset of vertically arranged drawers mounted in a frame by spaced drawerslides each having an outer slide member and an inner slide memberslidable relative to one another, the outer slide member being adaptedfor mounting on the frame and the inner slide member being adapted formounting on a respective one of the drawers, said interlock assemblylocated at the rear of each drawer slide on at least one side of the setof drawers, said interlock assembly comprising: a housing; a plateslidably movable within the housing between a first position and ablocking position; an actuator mounted on the rear of the inner slidemember; cooperating attachments on the plate and on the actuatorenabling the plate to be selectively engaged by the actuator to move theplate to its blocking position during an operation of opening the drawerto which the inner slide member is connected; a catch that maintains theplate in the blocking position; an actuator follower supported formovement relative to the outer slide member between a plate blockingposition and a blocked position, the actuator follower having a firstfollower surface arranged for selective contact by an actuating surfaceon the actuator and a second follower surface arranged for selectivecontact by an actuating surface on the plate, wherein, when the draweris opened, at least one of the first follower surface is contacted bythe actuating surface on the actuator and the second follower surface iscontacted by the actuating surface on the plate to move the actuatorfollower from the plate blocking position to the blocked position, saidactuator follower subsequently being maintained in said blocked positionwhile the drawer is open by the plate in the plate's blocking position,and wherein closing of the drawer causes the plate to be returned to itsfirst position, and the actuator follower to be returned to the plateblocking position; and a rod connected to the actuator follower andadapted to connect to a second actuator follower of a second,substantially identical interlock assembly used on a second, adjacentdrawer, wherein when the actuator follower is in the blocked position,the rod maintains the second actuator follower of the adjacent interlockassembly in a plate blocking position to maintain the plate of thesecond interlock assembly in its first position.
 2. An interlockassembly according to claim 1, wherein the actuator surface on theactuator contacts the first follower surface to move the actuatorfollower outwardly away from the longitudinal central axis of the outerslide member.
 3. An interlock assembly according to claim 2, wherein theactuator follower is maintained in its blocked position when the plateis held in its blocking position as a result of a latch op the platemoving to a latched position.
 4. An interlock assembly according toclaim 1, wherein the plate is slidably supported in a housing supportedwithin a rear end of the outer slide member for movement towards andaway from the rear of the outer slide member and wherein the blockingposition is spaced therefrom, and wherein the catch is provided betweenthe housing and the plate.
 5. An interlock assembly according to claim 4and further comprising spring means biasing the plate towards the rearof the housing, and wherein the catch extends between the housing andthe plate to hold the plate in its blocking position spaced from therear of the housing, the cooperating members being arranged to move theplate from the rear of the housing to its blocking position when theinner drawer slide member is initially moved from its rearmost positionwhen the drawer to which it is fitted is opened but being arranged tarrelease the plate when the plate is in its blocking position to allowthe drawer fully to open, said release occurring once the catch is in alatched position, the arrangement being such that when the drawer ismoved towards a dosed position and the actuator moves into the vicinityof the latched plate, the catch is released allowing the plate to moveunder its spring bias to the rear of the housing.
 6. An interlockassembly according to claim 4, wherein the housing is divided into arear pan and a forward part spaced from the rear part and wherein therear part is connected to the forward part by at least one slide railextending generally parallel to the longitudinal axis of the outer slidemember.
 7. An interlock assembly according to claim 6, wherein aslideway is provided on the underside of the plate and engages the oreach slide rail.
 8. An interlock assembly according to claim 6, in whicha front edge of the rear part of the housing is parallel with a rearedge of the front part of the housing, said two edges providing guidewalls for the actuator follower.
 9. An interlock assembly according toclaim 6, wherein two rails extend the full length of the housing andwherein the catch comprises an upstand at a forward end of one of therails and a latching nose on a forward end of the plate.
 10. Aninterlock assembly according to claim 9, wherein a front end of theplate has the latching nose and a portion of the cooperating memberssupported thereon, the latching nose being connected to the remainder ofthe plate by a thin section of plastics material acting as a pivot toallow the nose to pivot about an axis extending at right-angles to theplane of the plate.
 11. An interlock assembly according to claim 10,wherein the nose has a hook on a rear face thereof which co-operateswith a leading edge on the upstand to provide the catch.
 12. Aninterlock assembly according to claim 11, wherein a rear face of theupstand cooperates with a stop on the plate to limit movement of theplate away from a rear end of the drawer slide.
 13. An interlockassembly according to claim 9, wherein tire cooperating members comprisea stud on a rear face of the actuator which cooperates with a catchingsurface in a recess in the nose, the nose having a position of rest inwhich the hook is in a position to engage the forward end of the upstandand the arrangement being such that, when the actuator moves towards therear of the outer drawer slide member so as to overlie the plate, thestud will engage with a release surface opposite the catching surface tocause the nose to pivot in a direction so as to release the hook fromthe forward end of the upstand thus allowing the plate to move under itsspring bias towards the rear of the outer drawer slide member until theside surface of the plate will no longer prevent the actuator followerfrom moving towards the longitudinal central axis of the slide member.14. An interlock assembly according to claim 6, wherein the rear part ofthe housing is connected to the forward part of the housing by abridging member incorporating two outwardly turned rails with which arear portion of the plate engages, there being upstanding guide postslocated on a forward end of the forward part of the housing which act asguide means for a forward end of the plate.
 15. An interlock assemblyaccording to claim 14, wherein the forward end of the plate is providedwith laterally extending slide surfaces which engage beneath inturnedguides on the upstanding guide posts.
 16. An interlock assemblyaccording to claim 14, wherein the cooperating members comprise acentral aperture provided in the forward end of the plate receiving afirst part of the cooperating members.
 17. An interlock assemblyaccording to claim 16, wherein the first part of the cooperating membersis pivotally supported within the aperture by means of a pair ofoutwardly projecting pivots which engage within the mating pint slots inthe underside of the plate.
 18. An interlock assembly according to claim17, wherein the first part of the cooperating members comprises a mainspine which locates wholly within the aperture, the spine havingupstanding from its rear end an abutment and upstanding from its frontend a further abutment having a chamfered leading edge, there being aresiliently deformable latching hook extending from the undersidethereof.
 19. An interlock assembly according to claim 18, wherein agroove is formed on the rear face of the actuator which terminates in adepending block comprising a second part of the cooperating members andsized to fit between the abutment and the further abutment, a rear faceof the block being engageable with a forward face of the abutment and afront face of the block being engageable with a rear face of the furtherabutment, the arrangement being such that, as the actuator movesforwardly from a rear end of the outer drawer slide, the block willengage the rear face, thus drawing the plate against its spring biastowards a front end of the housing until a trailing end of the latchinghook engages with a front edge of the forward part of the housing,whereupon the block will disengage from the first part of thecooperating members to allow the drawer to open fully, and thearrangement being such that, when the drawer is moved rearwardly, therear face of the block will ride over the chamfered leading edge of thefurther abutment, allowing the actuator ti move rearwardly until theblock engages the forward face on the abutment, this causing the firstpart of the cooperating members to pivot so as to disengage the hookfrom the front edge of the housing, allowing the block to engage betweenthe abutment and the further abutment, and thereby allowing the plate tomove under its spring bias towards the rear end of the slide member. 20.An interlock assembly according to claim 14, wherein the spring bias isprovided by a coil spring extending between a buffer at the rear of thehousing and two spaced anchoring points on the underside of the plate.21. An interlock assembly according to claim 4, wherein a single sliderail joins together the front and rear parts of the housing and acentral slide way is formed in said slide rail having at a rear endthereof a recycling recess and adjacent a front end thereof a latchingrecess.
 22. An interlock assembly according to claim 21, wherein theplate has a central slide way on its underside which engages with theslide rail and wherein, within the central side way, a recess isprovided at one end with a pivot pin and at its opposite end with anarcuate slot whereby a pivoting arm having an aperture in one endthereof and a catch pin at the other end thereof is pivotally supportedin the recess with the aperture surrounding the pivot pin and the catchpin sliding in the arcuate slot and projecting upwardly therefrom. 23.An interlock assembly according to claim 22, wherein a depending guidepin is provided on the underside of the pivot arm for sliding engagementin the slide way in the slide rail on the housing.
 24. An interlockassembly according to claim 21, wherein the actuator has on itsunderside three principal recesses therein, two of which open laterallyoutwards and are partly defined by forwardly facing actuating surfacesdesigned to Cooperate with follower surfaces on the actuator followersand the third of which is located between two rearwardly facing inclinedsurfaces designed to cooperate with forwardly facing inclined followersurfaces on the actuator followers.
 25. An interlock assembly accordingto claim 24, wherein the third recess extends generally fore and aftwithin the underside of the actuator and has a downwardly dependingisland block therein spaced from the walls of the recess to define afore and aft extending linear channel on the side of the block and arecycling channel on the Other side, the fore and aft extending channeland the recycling channel being interconnected at a forward end of therecess by an arcuate wall of the recess, part of which defines anunlatching surface for the catch pin and another part of which forms arecycling camming surface for the catch pin.
 26. An interlock assemblyaccording to claim 25, wherein at its forward end, the island block hasan inclined pin pulling surface which merges with a front end of a latchactuation surface, the rear end of which merges with the fore and aftextending passageway.
 27. An interlock assembly according to claim 25,wherein a rearwardly facing recycling surface is provided on thedepending island block for moving the catch pin upwardly into therecycling recess in the slide way.
 28. An interlock assembly accordingto claim 1, wherein when the plate is in its blocking position, a sidesurface of the plate contacts the second follower surface of theactuation follower to prevent the actuator follower from moving backtowards its plate blocking position, thus maintaining the actuatorfollower of the adjacent drawer slide interlock assembly of the adjacentdrawer in such a position that it will prevent movement of the plate ofthe adjacent mechanism from moving to its blocking position, therebypreventing opening of the second drawer.
 29. An interlock assemblyaccording to claim 28, wherein the plate is delta-shaped with a forwardprojecting nose.
 30. An interlock assembly according to claim 29,wherein the leading edges of the delta-shape comprise the actuatingsurface on the plate.
 31. An interlock assembly according to claim 29,wherein the catch comprises the projecting nose.
 32. An interlockassembly according to claim 1, wherein the actuator has a furtherinclined surface on its trailing edge, relative to its forward movement,for cooperation with an inclined reset surface on the actuator follower.33. An interlock assembly according to claim 1, said interlock assemblyincorporating therein a self close mechanism for the drawer slide. 34.An interlock assembly according to claim 33, wherein the self closemechanism comprises a spring extending between a housing of theinterlock assembly and a plate movably supported in the housing andwhich plate is connected to the inner slide member of the drawer slideby latching means forming part of the interlock assembly when the innerslide member is adjacent the rear of the drawer slide.
 35. An interlockassembly according to claim 33, wherein the plate is slidably supportedin the housing between a first position at the rear of the housing and ablocking position spaced therefrom, the spring biasing the plate towardsthe first position at the rear of the housing.
 36. A stack of drawersarranged vertically in a cabinet, each drawer being mounted in a frameby spaced drawer slides each having an outer slide member and an innerslide member slidable relative to one another, the outer slide memberbeing adapted for mounting on the frame and the inner slide member beingadapted for mounting on a respective one of the drawers, and each drawerbeing provided with an interlock assembly located at the rear of eachdrawer slide on at least one side of the stack of drawers, the interlockassembly comprising: a housing; a plate slidably movable within thehousing between a first position and a blocking position; an actuatormounted on the rear of the inner slide member; cooperating attachmentson the plate and on the actuator enabling the plate to be selectivelyengaged by the actuator to move the plate to its blocking positionduring an operation of opening the drawer to which the inner slidemember is connected; a catch that maintains the plate in the blockingposition; an actuator follower supported for movement relative to theouter slide member between a plate blocking position and a blockedposition, the actuator follower having a first follower surface arrangedfor selective contact by an actuating surface on the actuator and asecond follower surface arranged for selective contact by an actuatingsurface on the plate, wherein, when the drawer is opened, at least oneof the first follower surface is contacted by the actuating surface onthe actuator and the second follower surface is contacted by theactuating surface on the plate to move the actuator follower from theplate blocking position to the blocked position, said actuator followersubsequently being maintained in said blocked position while the draweris open by the plate in the plate's blocking position, and whereinclosing of the drawer causes the plate to be returned to its firstposition, and the actuator follower to be returned to the plate blockingposition; and a rod connected to the actuator follower and adapted toconnect to a second actuator follower of a second, substantiallyidentical interlock assembly used on a second, adjacent drawer, whereinwhen the actuator follower is in the blocked position, the rod maintainsthe second actuator follower of the adjacent interlock assembly in aplate blocking position to maintain the plate of the second interlockassembly in its first position, wherein the rod is located adjacent therear of the cabinet.
 37. A method of preventing a stack of drawerssupported in a cabinet from toppling over as a result of more than onedrawer being opened at any one time, each drawer in the stack beingmounted in a frame by spaced drawer slides each having an outer slidemember and an inner slide member slidable relative to one another, theouter slide member being adapted for mounting on the frame and the innerslide member being adapted for mounting on a respective one of thedrawers, the method comprising fitting each drawer in the stack with adrawer slide interlock assembly comprising: a housing; a plate slidablymovable within the housing between a first position and a blockingposition; an actuator mounted on the rear of the inner slide member;cooperating attachments on the plate and on the actuator enabling theplate to be selectively engaged by the actuator to move the plate to itsblocking position during an operation of opening the drawer to which theinner slide member is connected; a catch that maintains the plate in theblocking position; an actuator follower supported for movement relativeto the outer slide member between a plate blocking position and ablocked position, the actuator follower having a first follower surfacearranged for selective contact by an actuating surface on the actuatorand a second follower surface arranged for selective contact by anactuating surface on the plate, wherein, when the drawer is opened, atleast one of the first follower surface is contacted by the actuatingsurface on the actuator and the second follower surface is contacted bythe actuating surface on the plate to move the actuator follower fromthe plate blocking position to the blocked position, said actuatorfollower subsequently being maintained in said blocked position whilethe drawer is open by the plate in the plate's blocking position, andwherein closing of the drawer causes the plate to be returned to itsfirst position, and the actuator follower to be returned to the plateblocking position; and a rod connected to the actuator follower andadapted to connect to a second actuator follower of a second,substantially identical interlock assembly used on a second, adjacentdrawer, wherein when the actuator follower is in the blocked position,the rod maintains the second actuator follower of the adjacent interlockassembly in a plate blocking position to maintain the plate of thesecond interlock assembly in its first position, whereby when a firstone of the drawers in the stack is opened, the interlock assembly of thefirst drawer will prevent the other drawers from being opened until thefirst drawer is moved to a closed position.